Safety envelope or letter openers have previously been proposed where a small blade is mounted on a body in a position projecting into a slot that passes through the body. The slot defines a channel that is closed on three of four sides around the slot axis, leaving an open fourth side to define a mouth of the slot for accommodating passage of an edge-adjacent portion the envelope through the slot from the one end to the other along the edge of the envelope the user wants to cut open. The blade projects from one closed side of the channel toward the opposing closed side at a distance outward from the third closed side that connects the first two, thereby placing a point formed at an end of the cutting edge in close proximity to the second side of the channel. An end of the edge-adjacent portion of the envelope is fed into an end of the slot with the edge of the envelope abutted up against the third wall for sliding therealong as either the tool is pulled along this edge of the envelope, or the enveloped is pulled through the slot. By moving the blade along this edge, or moving the envelope through the slot, the cutting edge cuts along the respective edge of the envelope during this relative sliding between the envelope and the tool channel.
Examples of such envelope openers are disclosed in U.S. Pat. No. 2,282,062 of Jewett, U.S. Pat. No. 2,247,840 of Harrison, and U.S. Pat. No. 4,873,767 of Lok.
In making and testing envelope openers of this general type, Applicant found that there is often a tendency for the tool to skip or ride off the edge of envelope during the process of running the tool over the envelope. Accordingly, there remains room for improvement, and applicant has developed a new envelope opener that addresses this complication, and provides additional advantages in terms of ease of use of the opener and convenient carrying of the unit on a keychain for readily available access.
U.S. Pat. No. 4,581,823 discloses another envelope opener for sliding along a peripheral edge of an envelope via a blade-containing channel of the opener, but differs from the forgoing examples in that the tool body is flexible and two legs of the tool body are pinched together in order to move the blade into a position reaching near enough to the opposing leg to cut into the envelope. Attaining a sufficient depth of cut without bunching-up of the envelope paper may be difficult, as the clearance between the cutting edge of the blade and the opposing leg of the flexible tool body is manually controlled by the pinching pressure applied between the thumb and forefinger of the user.
Another prior art letter opener is disclosed in U.S. Pat. No. 5,720,062, but differs notably from the designs referenced above and detailed herein below.